As a pilot, I've been around a lot of Decathlon's, Citabira's, Cub's, ect. Many times the ARF's or even kits are always way off when it comes to dimensions. Now sometimes, there's a reason for "taking liberties" with the scale dimensions. For example, lengthening the the fuselage or increasing the vertical stabilizer or rudder, takes some of the "touchy," "twitchy," characteristics of the "real" plane and make the model easier to handle. For example, a Pitts Special, which is a handful, because of it's short tail-moment, so sometimes it makes sense to make changes that would make the plane more enjoyable. I've had some scale models, that were a accident waiting to happen.

Now, guys correct my math. Here is a link to the current manufacture of the Decathlon/Super Decathlon specifications.
http://www.amerchampionaircraft.com/...th/sdspecs.htm

If we take the Length and divided by the wingspan you should get a number that tells the percentage of the wingspan to the length of fuselage. Then take the model's dimensions and do the same thing. If they Seagull used scale dimensions, then the percentage should be similar.

Real Plane
Super Decathlon Wingspan = 32ft
Super Decathlon Length = 22.9ft
Divide Length by Wingspan, I got just under 72%

The 120 Size Seagull Decathlon
Wingspan = 78.7"
Length = 52.9"
Dived Length by Wingspan, I got just over 67%

So, the model is a little short of scale, by 5% Nothing earth shattering!

Okay, I'll stop now! Just let me know if my math is wrong!